Load balancer Plug-in Problems During Side-by-Side Upgrade

While upgrading from Application Server 8.x EE to Application Server 9.1, during a side-by-side upgrade, you will not be able to point your new 9.1 load balancer plug-in to the old 8.x web server installation, if the load balancer plug-in is colocated with other Application server components on a single system. You need to install web server again and point the 9.1 load balancer plug-in installation to the instance belonging to the new installation.